#define  _CRT_SECURE_NO_WARNINGS
#include <stack>
using namespace std;


class Solution
{
public:
    void push(int node) {
        stack1.push(node);
    }

    int pop() {
        while (!stack1.empty())
        {
            stack2.push(stack1.top());
            stack1.pop();
        }
        int ret = stack2.top();
        stack2.pop();
        while (!stack2.empty())
        {
            stack1.push(stack2.top());
            stack2.pop();
        }
        return ret;
    }
private:
    stack<int> stack1;
    stack<int> stack2;
};

class Solution
{
public:
    void push(int node) {
        stack1.push(node);
    }

    int pop() {
        if (stack2.empty())
        {
            while (!stack1.empty())
            {
                stack2.push(stack1.top());
                stack1.pop();
            }
        }
        int ret = stack2.top();
        stack2.pop();
        return ret;
    }

private:
    stack<int> stack1;
    stack<int> stack2;
};